Hello all, this is my first post so bear with me. On saturday (6/27) I'll be travelling from Cincinnati to LAX with a stop in Minneapolis. The first leg will be operated by Delta/Comair and the second by Northwest. I'd really like to try and purchase an upgrade to business class for the Northwest flight. I'm not a WorldPerks member but I'm a SkyMiles member, but only have around 5000 miles, and I'll have to check-in at a Delta kiosk...how might I go about purchasing this upgrade if at all possible?

Thanks